I really like those wheels! How much do the choppers run you? Also, you realize that you can't run AWD with it either, right? I love RWD, and my xmod is staying RWD (I did AWD, and it's fun, but I like a challenge driving with my brushless). Right now, I'm using Mini-Z rear wheels, which are 11mm wide as opposed to the stock 9mm wide wheel, and they have a ton of tire options. Right now, I'm using a fairly sticky set of 20s (kyosho actually calls them 40s, but everywhere I look they're rated 20 less than what kyosho rates them). The adapter setup I did for it was pretty straightforward and required the sacrifice of 2 Skyline wheels. Those skinnies are really cool too. Di you just take down the width but leave the backspacing? If you machined down the backspacing, I'd think you'd run into problems with it being loose. Here's pics of my little setup:
Mmmmmmm, meaty:
